Protective device for lithographic press

ABSTRACT

A protective device for a lithographic press used for lithographing metal sheets to minimize damage resulting from defective sheets or jam-ups. The protective device includes a spring-biased rocker assembly having stripper fingers which are disposed to permit uninterrupted travel of the metal sheets between the blanket cylinder and the impression cylinder when the leading edge of the metal sheets is gripped by gripper fingers mounted on the impression cylinder. When the leading edge of a metal sheet is not gripped by the gripper fingers, the stripper fingers guide the metal sheet into engagement with means for rocking the rocker assembly out of the normal position. Upon rocking of the rocker assembly the power to the press is cut off.

United States Patent 1 [21] Appl. No.

[72] Inventor Harry H. Mclntire Portland, Oreg.

Nov. 12, 1968 Jan. 12, 1971 Continental Can Company, Inc. New York, N .Y.

a corporation of New York [22] Filed [45] Patented [73] Assignee [5 4] PROTECTIVE DEVICE FOR LITHOGRAPHIC ESS PR 5 Claims, 4 Drawing Figs.

[52] US. Cl 101/233, 271/47, 271/57 [51] Int.Cl B41fl3/24 [50] Fiel oi'Search 101/233, 2314;271/47, 56, 57 [56] References Cited UNITED STATES PATENTS 655,963 8/1900 Dexter et a]. 271/56 1,114,020 10/1914 Niles 101/233 1,469,515 10/1923 Kelly 271/56 2,395,740 2/1946 Hileman et al.... 271/56UX 3,056,134 9/1962 Beyer lO1/233X 3,185,473 5/1965 Miaskoffet al. 27l/56 Primary Examiner-Robert E. Pulfrey A ssislant Examiner Clyde Coughenour Attorneys-Fred P. Kostka, Joseph E. Kerwin and William A.

Dittmann ABSTRACT: A protective device for a lithographic press used for lithographing metal sheets to minimize damage resulting from'defective sheets or jam-ups. The protective device includes a spring-biased rocker assembly having stripper fingers which are disposed to permit uninterrupted travel of the metal sheets between the blanket cylinder and the impression cylinder when the leading edge of the metal sheets is gripped by gripper fingers mounted on the impression cylinder. When PATENTED-JAN 1219?:

SHEEI 1 OF 2 V INVENTOR ATT'Y.

PATENT EU JAN 1 21am SHEET 2 or 2 INVE N TOR RX H IIVTI/PE' svmj g/ 0 ATT'Y.

. rnorucr'lvn'nevics rontrrnoennnic amass Q BACKGROUNDOF THEINVENTIQN'Y The presentinvention relates toglithographio p es'ses of the type used for printing onmetalisheets-and more particularly,

to a protective device for v sueh lithographic-pressesto reduce the damagethereto resulting from ja m ups or defective sheets.

Lithographic pressesofthetypeto which the present invention relates comprise generally aLpress rollerhaving a ,press plate mounted thereon f l'hegink-li's initially deposited on the press roller and-transferred to a blanket cylinder which coacts with an impression "cylinder mountedfor movement toward and away from the blanket cylinder; The blanketandimpression cylinders areboth-rotatablylmountedand are operative to s a metal n a e ee hmu h :J-t.

topass therebetweem; Thel timin'giot'; the-press is such thatthe transferred or offset inkimage onthe' blanketcylinder contactsthe surfaceof the plate during thefeed-through so that the plate receives theink' design from the.hlanket surface. conventionally, the lithographic, press ,ihcludes: a", detectormeans'locatedfon the feedtable, wliic rqesto lowerthe'impression cylinderawayfroinltheblanke ylindercshould a gap occurin the flow of plate.to,the pressas' by way ofthe feeder failing to supply a sheet or causea doublesheet rejectiomThe pression cylinder fromjpicking up the inked image on the blanket cylinderand printingitonthe bottom side ofthe next plate .sheetfedthrough uf.

The plate sheets, aftersreceiving the inked image from the I blanket cylinder, are discharged fromthe press and moved by conveyor tapes tola trailing coatenwhiehapplies a protective coating of clear varnish over thefi'nish of; the plate. From the coater the sheets areconveyed by. tapes and deposited-in a wicket conveyor assembly-and moved into'an oven for a baking operation which 'rapidlydries the inkiand varnish. L

. While thesafety device on'the input side of the cylinders is satisfactory to reduce damage to theirnpression cylinder, difficulties have been encountered in preventing damage to the press resulting from jamming'or defective plates arriving at the impression and blanketcylinders. During the operation of the lithographic press, a'defective' platesuch'as a bent plate or short plate may pass undetected beyond the detector device on the input side of the rollers. Under these iconditions,the

Thisis accomplished generally by the provision of a springbiasing rocker assembly mounted on the'discliarge side of the impression and blanket cylinders. The rocker assembly includes stripper finger means which are disposed in the normal path of travel of the metal plate when the latter is gripped by predeter- I the gripper fingers to provide a guide path away from the blan- .ket cylinder. Should, however, the metal plate not be gripped by the gripper fingers, thestripper fingers are operative to guide the metal plate intolengagemeht with the rocker assembly so that the latter is displaced outof the normal position thereof. In the displaced position the rocker assembly is operative to shut off the drive to the cylinders.

BRIEF DESCRIPTION ()F THE DRAWINGS FIG. .1 is a fragmentary perspective .view of the blanket 7 cylinder and impression'cylinder of a lithographic press and .showing the protective device of the "present invention mounted thereon; n t FIG. 2 is a front elevational view of the protective device as- I FIG. 3 is a cross-sectional view of the protective device taken generally along the lines 3-3 of FIG. 2; and

.FIG. 4 is a cross-sectional view of 'the protective device taken generallyalong the lines 4-4 of. FIG. '2. e 7

:Referring now to the drawings, in particular 16.1, there is shown a fragmentary view of a lithographic printing press 10 incorporatingthe protective device 1 of the present invention. As shown, the lithographic printing press 10 includes a blanket cylinder 12 and an impression cylinder 13, each being mounted for rotation between frame members 144 and 14b. The cylinders 12 and 13 areboth driven by a gear drive (not .shown) of conventional structure.,The gears are operated by a power supply such as an electric motor,

The blanketcylinder 12 is of substantially standard con struc'tion and includes a blanket:l6 which receives the impresdetector device in this manner prevents the surfaces of the imsion or image to be printed on the metal sheets 17.which travel between the cylinders 12 and 13 from a press roller (not shown). The blanket 16 may be made from rubber orthe like.

The impression cylinder 13 is supported for movement toward and away from the blanket cylinder 12 to press the metal sheetl7 against the blanket cylinder 12. The impression cylinder supporting means is of the well known standard construction, and it is believed that a'fu'rther description is not necessary for an understanding of the present invention. The impression cylinder 13 during normal operation or printing of .the sheet 17 is in pressing engagement with the blanket 50 cylinder 12 and drops to a position spaced therefrom so that the image or ink is'not transferred to the blanket surface 16 when metal sheets 17 are not passing between the cylinders 12 and 13.

The metal sheets 17 tovbe imprinted on one side are fed to the impression and blanket cylinder station by pusher means (not shown) of suitable standard construction. The sheets 17 are delivered in timed relationship so that there is a predetergripper fingersonthe impression cylinder may not engage with the leading edge of the defective plate so that the'plate is not pulled through the rollers. As a result, a following plate may enter into the input side of the rollers and be jammed x therebetween. Sucha jam-up createsdamage to the blanket cylinder by either destroying the surface thereof so that it must be replaced, or it may-damage the impression cylinder. A jam-up or defective sheet-condition is manifested by the failure of the gripperfingers on the-impression cylinder to grip a leading edge of the plate to pull-it through the blanket cylinderand impression cylinder.

. By the present invention it isproposed to provide a protective device which is operative to detect'when the gripper finbetween the blanket cylinder 12 and'impression cylinder 13 mined spacing therebetween. Should the sheets 17 not be in a single layer or be spaced a distance greater than that determined by the timed relationship, the detector switch (not shown) on the input side of the cylinders 12 and 13 will detect the same and stop operation of the press 10. During the stop period as above explained, the impression cylinder 13 moves away from the blanket cylinder 12. v

Upon engagement with the impression cylinder 13 the leading edge 15 of the sheets 17 is grasped by gripper fingers 18 mounted therein. The gripper fingers 18 are cam actuated in standard manner and are operative to pull the sheets 17 until the friction between the same is operative to further feed the metal sheet 17 through the cylinders 12 and 13. As shown gers fail to grip the leading edge of the plates so as to deenergize the powersu'pplyto the press andthereby prevent, press .damage when a'defective sheet, or' 'jam-up occurs atthe impression and blanket cylinders. ,7

in FIG. 3, the gripper fingers 18 are released in a position spaced outboard of the point of engagement of the impression cylinder 13'and blanket cylinder 12. In this connection it is to benoted that the leading edge 15 of the metal sheet 17 is disposed downwardly and away from the surface of the blanket cylinder 12 so that the edge thereof does not dig into the rubber blanket 16 on the blanket cylinder 12.

Under some circumstances the detector switch on the input side of the cylinders 12 and 13 will not detect the presence of a defective sheet or the presence of a double-sheet thickness passing thereover. Under these circumstances, the sheet will pass between the cylinders 12 and 13 and the sheets 17 will jam between the cylinders or, alternatively, dig into the rubber blanket 16 so as to damage the latter and require replacement.

In accordance with the present invention, the protective device 11 prevents the damage to the cylinders as occurred heretofore. Under the circumstances in which either a defective sheet or a multiple sheet thickness is disposed between the cylinders such that the gripper fingers 18 do not grasp the leading edge 15 of the sheet 17, the protective device 11 is operative to stop the operation of the press and to cut off further rotation of the cylinders. Thus, the failure of the gripper fingers 18 to engage with the leading edge of the metal sheets 17 is utilized to initiate or trigger the operation of the protective device 11, as more fully to be explained hereinafter.

The protective device 11 comprises generally a rocker assembly 20 comprising a pair of laterally spaced rocker arms 21 and 22. The rocker arm 21 at its lower end is pivotally supported by means of a pivot stud assembly 23 which is fastened at one end to the frame member 14b. The rocker or lever arm 22 at its lower end is pivotally connected to the opposite side of the frame 14a by means of a pivot stud 24. Fixed to the upper end of the rocker arm 22 is one end of a horizontally disposed plate 26, to the other end of which there is fixed an upstanding arm 27.-The arm 27 terminates at substantially the same level as the rocker arm 21. Disposed and fixed between the upper ends of the rocker arm 21 and the arm 27 is a shaft 28. Securing the ends of the shaft 28 to the respective arms 27 and 21 are clamp assemblies each comprising a clamping block 29 fixed to the upper end of the bars 27 and 21 respectively as by welding and a complementary removable clamping block 31 which is fastened to the clamping block 29 by means of bolts 32.

Spaced lengthwise and mounted on the shaft 28 are a plurality of stripper fingers 33. Disposed between and spaced lengthwise of the shaft 28 and fixed thereto there are also a plurality of trigger or stop fingers 34. The structure in function of the stripper fingers 33 and trigger fingers 34 will be more fully explained hereinafter.

For holding the shaft 28 and the stripper fingers 33 and trigger fingers 34 fixed thereto in the normal operative position there is provided a spring-biased positioning subassembly 36. The spring-biased subassembly 36 comprises a cam lever 37 pivotally connected at one end by means of a pivot stud 38 to the frame 14a. At its other end the cam lever 37 is formed with an inclined camming face 39 which engages the edge of the horizontal plate 26. Pivotally connected intermediate the ends of the cam lever 37 by means of a bolt and nut assembly 40 is a yoke 41 to the upper end of which there is fixed the lower end of a shaft 42. The upper end of the shaft 42 is slidably supported by a sleeve 43 which is fixed to the frame 14. Disposed between the underside of the sleeve 43 and the upper face of the yoke 41 is a biasing spring 44. The biasing spring 44 serves to apply a downward force on the camming lever 37 so that the camming face 39 at one end thereof is in engagement with the horizontal plate 26 to bias the rocker assembly 20 toward the full line position shown in FIG. 4. Fixed to the arm 22 substantially intermediate the ends thereof is a stop plate 46 which engages a complementary stop or lug 47 provided on the frame 14a so that further movement of the rocker assembly 20 is limited thereby. 1n the position shown in FIG. 4 the right end clamping block 29 engages a roller 48 ofa microswitch 49 mounted on the frame 14. The microswitch 49 is suitably connected into the power circuit for operating the press 10 so that, upon disengagement of the clamping blocks 29 and 31 with the roller 48, power is cut off to the press 10 to stop the latter.

As shown in particular in FIG. 3, the stripper fingers 33 are each fixedly clamped to the shafi 28 and are of substantially triangular contour at one end thereof and include an upper substantially flat edge 51 and a lower tapered knife edge 52 which merge to form an apex 53. The apex 53 is disposed in the space closely adjacent the output or plate discharge end of the impression cylinder 13 and the blanket cylinder 12. As shown, the knife edge 52 is spaced sufficiently from the impression cylinder 13 to provide a passage 50 for projecting gripper fingers l8 and the metal sheets 17. It is to be noted that the leading edge 15 of the metal sheet 17 is released from the gripper fingers 18 when the sheet 17 is disposed below or past the apex 53. In this manner the stripper fingers 33 engage the sheets 17 so as to strip the sheet 17 from the blanket cylinder 12 by overcoming the cohesive forces acting between the ink deposited on the sheet 17 by the blanket cylinder 12 and guide the sheet 17 into the passage 50.

Should the gripper fingers 18 not engage the sheet leading edge 15 as, for example, caused by a defective plate or 20 jamming as a result of multiple plates being fed between the cylinders, the cohesive force of the ink acting between the sheet 17 and the blanket cylinder 12 will tend to curl the leading edge 15 upwardly and over the upper flat edge 51 of the stripper fingers 33 into a passage 54 defined-between the flat edges 51 and the periphery of the blanket cylinder 12. Located in the path of movement of sheet 17in the passage 54 are the stop fingers 34. The stop fingers 34 are fixedly clamped to the shaft 28 and include an upwardly inclined leg 55 which terminates in an upstanding leg 56. When the sheet leading edge 15 engages the leg 56, a force is exerted thereon so that the rocker assembly 20 is moved clockwise as viewed in FIG. 4 against the force of the biasing spring subassembly 36. As the rocker arm assembly 20 moves clockwise, the horizontal plate 26, in engagement with the camming face 39 of the camming levr 37, rotates the latter counterclockwise about the pivot pin 38 against the force of the biasing spring 44.

When the rocker assembly 20 rotates clockwise, the clamping block 29 fixed to the rocker assembly 20 moves out of engagement with the roller 48 of the microswitch 49 so that the power drive to the cylinders 12 and 13 is rendered inoperative. The main switch may then be deactivated, and the condition causing the protective device 11 to be operative is corrected by removing 'the damaged sheets 17. Upon removal of the sheets 17 from the passage 54, the biasing spring 44 acting on the camming lever 37 rotates the latter counterclockwise. At the same time the lever camming face 39 in engagement with the plate 26 of the rocker assembly 20 returns the latter to the normal operating position so that the stop plate 46 engages the stop lug 47. The microswitch 49 is then energized by engagement of the clamping block 29 therewith. Thus, upon actuation of the man switch, the press 10 is again operative to continue the printing of the metal sheets 17.

lclaim:

l. A protective assembly for a lithographic printing press including a rotatable blanket cylinder and a rotatable impression cylinder having gripper means engageable with the leading edge of single metal sheets delivered to said cylinders for pulling said single sheet between said cylinders and releasing said single sheet leading edge when the latter extends outwardly of said discharge side of said cylinders, said protective assembly comprising a rock arm assembly rockable from a first position permitting operation of said press to a second position cutting off operation of said press, stripper finger means mounted on said rock arm assembly and disposed on the discharge side of said cylinder, said stripper finger means in said first rockable position having surface means disposed in spaced relationship to said blanket cylindersurface and said impression cylinder surface to provide a first guiding path through which said metal sheets travel away from said blanket cylinder when said gripper means grip said leading edge of said sheets and a second guiding path through which said sheets travel when said sheets are not gripped by said gripper fingers, stop means fixedly mounted on said rocker assembly biased subassembly yieldably retains said rock arm assembly in saidfirst position and said rock arm assembly moves to said second position against the force of said spring-biased subassembly.

3. The invention as defined in claim 2 wherein said stripper finger means are each of substantially triangular contour and include an apex extending toward the line, of contact of said blanket cylinder and said impression cylinder, and one side of said triangle forming said apex definessaid first guide path and the other side defines'said second guide path.

4. The invention as defined in claim 3 wherein said one side of said stripper finger is in the form of a knife edge, and said other side is a substantially planar face. I

5. The invention as defined in claim 4 wherein said stop means includes a stop surface projecting above said planar face of said stripper finger means. 

1. A protective assembly for a lithographic printing press including a rotatable blanket cylinder and a rotatable impression cylinder having gripper means engageable with the leading edge of single metal sheets delivered to said cylinders for pulling said single sheet between said cylinders and releasing said single sheet leading edge when the latter extends outwardly of said discharge side of said cylinders, said protective assembly comprising a rock arm assembly rockable from a first position permitting operation of said press to a second position cutting off operation of said press, stripper finger means mounted on said rock arm assembly and disposed on the discharge side of said cylinder, said stripper finger means in said first rockable position having surface means disposed in spaced relationship to said blanket cylinder surface and said impression cylinder surface to provide a first guiding path through which said metal sheets travel away from said blanket cylinder when said gripper means grip said leading edge of said sheets and a second guiding path through which said sheets travel when said sheets are not gripped by said gripper fingers, stop means fixedly mounted on said rocker assembly in the path of movement of said sheets through said second guiding path means and engageable therewith so that said rock arm assembly is rocked out of said first position to said second position, switch means operative to deactivate said blanket cylinder and said impression cylinder when said rock assembly moves from said first position to said second position.
 2. The invention as defined in claim 1 wherein a spring biased subassembly yieldably retains said rock arm assembly in said first position and said rock arm assembly moves to said second position against the force of said spring-biased subassembly.
 3. The invention as defined in claim 2 wherein said stripper finger means are each of substantially triangular contour and include an apex extending toward the line of contact of said blanket cylinder and said impression cylinder, and one side of said triangle forming said apex defines said first guide path and the other side defines said second guide path.
 4. The invention as defined in claim 3 wherein said one side of said stripper finger is in the form of a knife edge, and said other side is a substantially planar face.
 5. The invention as defined in claim 4 wherein said stop means includes a stop surface projecting above said planar face of said stripper finger means. 